A. Field of the Invention:
The present invention relates generally to water heating devices, such as water heaters and boilers and to an improved finned copper tube water heater.
B. Description of the Prior Art
Water heaters and boiler (referred to collectively as water heaters in the discussion which follows) typically have a water heater tank, often of the vertical tube type which utilizes fire tubes located above a combustion chamber. The typical prior art gas, oil or gas/oil fired water heater featured a non-pressurized, external combustion chamber which was typically located on the bottom exterior of the water heater. Vertical shell or V-shell heat exchangers of the above type are well-known in the industry.
Water heaters of the above type generally provide for the flow of hot gas through a series of tubes mounted in vertical fashion between top and bottom support plates within the water heater tank. The products of combustion from the combustion chamber pass vertically upward through the upward interiors of the vertical tubes and out a flue outlet. Water is circulated into and out of a chamber in the prior art devices located between the tube support plates. The water contacts and circulates about the exterior of the vertical tubes to effect heat transfer to heat the water.
In U.S. Pat. Nos. 4,465,024; 4,545,329 and 4,938,204, water heater designs are shown which feature one or more submergible, pressurized combustion chambers so that all combustion takes place in the water heater tank interior in a chamber surrounded by water. These improved water heater designs featured an externally mounted, forced draft burner unit mounted on the exterior of the closed tank at a tank opening so that the burner nozzle extends in the direction of the combustion chamber for heating the combustion chamber. The resulting designs decrease heat loss and increase the thermal efficiency of the water heater many times over that which was achievable with the prior art tube and plate arrangement.
A variety of heat exchanger designs are also known which feature, e.g., coiled tube heat exchangers. In such designs as the Legend Burkay from A. O. Smith Corporation of Milwaukee, Wis. water flows through the interior of the heat exchanger tubes while hot products of combustion flow over the outside of the heat exchanger. Certain of the prior art designs in which the water flow was through the tube interior featured finned copper tubes in combination with separate baffle elements. Other manufacturers of similar products, besides A. O. Smith Corporation, include Teledyne LARS Corporation, Lochinvar Corporation, RBI Water Heaters, Ray Pak, and Patterson-Kelley Corporation.
Despite the above noted improvements in water heater and boiler designs, a need has continued to exist for an improved water heater of the finned copper tuber variety which could be produced economically and which would be effective for heating potable water for end use applications, or for heating non-potable water for the purpose of, e.g., transferring heat to an air space or to a process, such as for food or chemical processing or other similar water heater and boiler applications.
A finned tube water heater which may be used to heat water or other heat transfer fluid and may be used as a heating boiler is shown which includes at least two flow manifolds, each having a water inlet and a water outlet and a plurality of connecting openings. A plurality of circular flow tubes are arranged in stacked fashion to form a tube bundle which surrounds an initially open interior space. Each flow tube has a pair of opposing connecting ends which connect to selected ones of the openings provided in the flow manifolds. A burner is also provided having a burner outlet which communicates with the interior space within the stacked tube bundle for producing products of combustion for heating water flowing in the flow tubes. The flow tubes have external fins located on an exterior surface thereof. The external fins are crushed to form upper and lower flat stacking surfaces for stacking the tubes to form the tube bundle. The external fins are also crushed to form angled baffled surfaces about an external periphery of the flow tubes. The baffle surfaces serve to retain heat from the products of combustion which are released into the interior space within the stacked tube bundle.
Preferably, the external fins which are crushed to form the angled baffled surfaces on each flow tube present a continuous exposed surface on the exterior of the tube bundle when the flow tubes are stacked in vertical fashion. The continuous exposed surface comprises an integral baffle surface for the tube bundle when the tubes are stacked with the flat stacking surfaces in contact, thereby eliminating the need for a separate baffle member to assist in retaining and more uniformly distributing heat from the products of combustion in the interior space within the stacked tube bundle. In the most preferred embodiment, each finned flow tube is formed with a forming die which creates four facets on the exterior of each tube. Two of the facets form the stacking surfaces and two of the facets form the baffle surface.
In the preferred embodiment of the invention, a pair of vertically arranged flow manifolds are provided, each having connecting openings for receiving a connecting end of the finned flow tubes making up the tube bundle as previously described. The pair of vertically arranged flow manifolds have internal passageways for cross communication between the flow manifolds, whereby water enters an inlet of the first manifold of the pair and circulates through an internal passageway and through a connected flow tube to the second manifold of the pair. Each traverse of water from one manifold to the other is characterized as a xe2x80x9cpassxe2x80x9d and the number of passes may range from one to many. The water then circulates through an internal passageway and through a second flow tube back to the first flow manifold. The circulation continues through all of the flow tubes until the water exits an outlet of one of the selected flow manifolds. A flow control switch can be located within a selected one of the vertically arranged manifolds in-line with the flow path of water through the flow manifold.
The tube bundle is constructed by positioning at least one brazing ring about each flow tube connecting end. The brazing ring is received upon an internal landing area of the flow opening in the flow manifold for brazing the tubes to the flow manifold. Preferably, the vertically arranged manifold and connected flow tubes are brazed in an furnace as a unit in a one-step brazing operation. Preferably, the tube bundle is brazed in a furnace in an oxygen starved atmosphere at a temperature in the range of about 1400xc2x0 Fahrenheit.
The tube bundle is sandwiched between a base pan and bulkhead, each of which can be provided with an insulating refractory disk for reducing heat loss through the base pan and bulkhead. The base pan and the bulkhead are joined by a plurality of connecting rods which hold the tube bundle, base pan and bulkhead in tension. In this embodiment, a one piece jacket, which can be insulated, circumscribes the tube bundle, base pan and bulkhead. The one piece jacket may be segmented to facilitate manufacture, assembly or services. The jacket seals against peripheral surfaces of the base pan and bulkhead to create a flue space when installed about the tube bundle. The flue space receives products of combustion produced by the burner. The jacket also has a flue outlet opening for exhausting products of combustion and may have an opening or openings for other piping penetrations. The one piece jacket can be held in place by a mechanical clasp and connectors, whereby the jacket is easily removable to expose the tube bundle and other components of the assembly for maintenance operations.
A blower/mixing box is mounted on an upper surface of the bulkhead. A burner retention flange is sandwiched between the blower/mixing box and the bulkhead. The blower/mixing box contains an internal scroll and an orifice member which together form a venturi passage. The internal scroll and orifice member have side tabs which are received within mating holes provided in the opposing sides of the blower/mixing box, alignment of the tabs and holes serving to provide the desired shape for the scroll within the blower/mixing box. Air and gas mixing, necessary for proper combustion, takes place within the blower/mixing box assembly, thus eliminating the need for separate down stream mixing contrivances. The blower/mixing box has an air inlet which may be fitted with an inlet damper system capable of responding to operational controls and which may provide indication of damper position. One embodiment of this inlet damper system has an internal butterfly member which is angularly positionable to control the flow of air through the assembly. The butterfly is movable between an open position for high fire conditions and a closed position for low fire conditions of the water heater, whereby the damper, in conjunction with a low and high fire valve or valves serves as a staging mechanism for the water heater.
An electrical control box with opposing sidewalls is mounted on the bulkhead. The one-piece jacket is provided with a control panel opening and a control panel is mounted within the opening. The control panel has a pair of opposing tabs at an upper end thereof which are received within mating T-slots provided in the opposing sides of the electrical control box. In this way, the control panel is positionable between a lowered positioned and an upwardly raised and locked position which provides access to electrical connections located within the electrical box. A transparent cover panel fits over the control panel within the control panel opening. The transparent cover panel is formed of a flexible plastic which allows the panel to be secured within the control panel opening by flexing the sides of the plastic material.
The gas train consists of one or more gas circuits with one or more gas valves per circuit. In one embodiment, the gas train consists of a one inch main control train for single stage models and an additional three-quarter inch control train for two-stage models. Both gas trains inject gas into the blower/mixing box where it is mixed with a combustion air supply. The combustion process is initiated by a hot surface spark or gas pilot ignitor adjacent to the burner. Desired water temperature is monitored to provide a controlling signal to turn on, control, and turn off the water heater.
Additional objects, features and advantages will be apparent in the written description which follows.